The present invention relates to a sealing web comprising a support layer in the form of a scrim, a woven fabric or a non-woven material, both surfaces of which are covered with a bituminous coating, an adhesive layer disposed on one surface thereof and a cover sheet.
Conventional roof sealing webs which are employed, in particular, for covering flat-roof structures, comprise a support layer which is covered on both sides with a bituminous coating. These bituminous composite webs are also often used as sealing webs for subterranean structures such as, for example, tunnels, and typically include an additional foil or sheet layer made of metal or plastic.
The support layers and/or reinforcing inserts employed for the bituminous roof sealing web comprise sheet-shaped articles in the form of woven fabrics or scrims, such as glass fiber mats or the like, but in particular also random non-woven materials made of polymer fibers or threads, for example of a polyester material, which are bonded in an appropriate manner. Random non-woven materials preferably are used because, compared with woven fabrics, they have good elastic properties, independent of any particular stretching direction.
Roof sealing webs of this kind are fabricated in a simple way by passing the support material, preferably a spun-bonded fabric, through a bitumen bath at elevated temperatures. In the process the support material is both impregnated and coated and, as a result, a multilayer article is obtained, which has an inner layer formed of the support material and outer layers comprising bitumen or modified bitumen. Such roof sealing webs are known in the art and are described, for example, in DE-C-31 45 266 and DE-A-34 05 109.
In order to be able to form the bituminous roof sealing webs into rolls and, above all, to permit unwinding of the rolls formed of the bituminous webs, particulate inorganic materials, such as talcum, sand or slate are usually spread on the inherently sticky bituminous surfaces. When the roof sealing web is fixed in place according to the welding process these release media have, however, the disadvantage that they considerably impair firm bonding of the roof sealing web to the roof. Bubble formations are then frequently observed, which eventually produce leakages.
For laying out and attaching the bituminous sealing webs to the surfaces to be sealed (roofs, cellar walls, bridge constructions, etc.) two process variants are basically known. On the one hand, it is possible to use the flame method, in which one surface of the sealing web is molten with the aid of open flames in the process of laying out the web and the sealing web is then bonded to the base by means of this molten surface; on the other hand, the casting method can be used, in which the sealing web is bonded adhesively to the base with the aid of bitumen or tar which has been heated beyond its melting point. The two methods have been described in bulletins by Messrs. Boerner (Bad Hersfeld, Nuernberg and Dietzenbach, Federal Republic of Germany). In more recent times, a cold-bonding method occasionally is employed.
The present invention is based on sealing webs which are fixed in place according to the cold-bonding method. The adhesive layers conventionally used comprise pressure-sensitive adhesive layers on a basis of caoutchouc or artificial butadiene polymers. Such permanently adhesive layers have, however, the disadvantage that a web which has been coated with an adhesive layer of this kind on one side thereof and then wound up into a roll can no longer be drawn off from the roll, because the front and the back of the web permanently stick together.
In order to obviate the above-described disadvantage, the free surface of the adhesive layer must be provided with a cover sheet which can be removed easily prior to laying out the web on the base. Within the scope of the present invention, the term "cover sheet" thus refers to a release layer which is applied to the free surface of the adhesive layer of the bituminous sealing web and prevents the sticking together of the individual layers of a roll formed of the sealing web. When the sealing web is drawn off from the roll the cover sheet remains as an integral part on the side of the sealing web to which it was originally applied, but is removed prior to actual application, i.e., laying out the sealing web on the base to be sealed.
Conventionally employed cover sheets comprise a silicone-treated kraft paper or a silicone-treated polyolefin film. These cover sheets, however, have the drawback that they easily tear when they are peeled off from the adhesive layer and that their resistance to tear propagation is very unsatisfactory. This often leads to highly inefficient delays in the process of laying out the sealing webs.